linux-kernel - Re: [PATCH v1] arm64/mm: Fix Boot panic on Ampere Altra

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Message-Id: <174052227763.2420464.2784848656225511807.b4-ty@kernel.org>
Date: Thu, 27 Feb 2025 18:50:27 +0000
From: Will Deacon <will@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Luiz Capitulino <luizcap@...hat.com>,
	Ryan Roberts <ryan.roberts@....com>
Cc: kernel-team@...roid.com,
	Will Deacon <will@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] arm64/mm: Fix Boot panic on Ampere Altra

On Tue, 25 Feb 2025 11:46:36 +0000, Ryan Roberts wrote:
> When the range of present physical memory is sufficiently small enough
> and the reserved address space for the linear map is sufficiently large
> enough, The linear map base address is randomized in
> arm64_memblock_init().
> 
> Prior to commit 62cffa496aac ("arm64/mm: Override PARange for !LPA2 and
> use it consistently"), we decided if the sizes were suitable with the
> help of the raw mmfr0.parange. But the commit changed this to use the
> sanitized version instead. But the function runs before the register has
> been sanitized so this returns 0, interpreted as a parange of 32 bits.
> Some fun wrapping occurs and the logic concludes that there is enough
> room to randomize the linear map base address, when really there isn't.
> So the top of the linear map ends up outside the reserved address space.
> 
> [...]

Applied the reduced version to arm64 (for-next/fixes), thanks!

[1/1] arm64/mm: Fix Boot panic on Ampere Altra
      https://git.kernel.org/arm64/c/2b1283e1ea9b

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev